1. Field of the Invention
The present invention relates to polybutylene glycol dimethacrylate and also to a resin composition for cast polymerization containing the same. More particularly, the present invention relates to polybutylene glycol dimethacrylate and also to a resin composition for cast polymerization containing the same, which are useful for the production of plastics having high heat resistance, good flexibility, and low water absorption.
2. Description of the Prior Art
At present, plastics find use in a variety of fields as molding materials, optical lenses, optical discs, electric and electronic parts, film, machine parts, and laminated glass. Plastics for these applications are required to have improved toughness, flexibility, and impact resistance. This requirement is met by incorporating polymer chains with polyether, polyurethane, polyester, or polycarbonate which has an elastic structure. The incorporation is carried out in the stage of monomer or oligomer prior to polymerization. There are application areas where plastics are required to be moisture-resistant. This requirement is met by incorporating polymer molecules with hydrocarbon chains, aromatic rings, halogen atoms. etc.
In the case where a polymer is produced by cast polymerization, it is desirable to use a monomer of low viscosity for good workability. This requirement is met when the polymer molecular chain has the polyether structure which is highly elastic. This polyether structure is imparted by polyethylene glycol di(meth)acrylate or polypropylene glycol di(meth)acrylate. The flexibility of polymer increases in proportion to the number of such repeating units as ethylene oxide and propylene oxide contained therein.
Although it is possible to lower the water absorption of a polymer by incorporating it with hydrocarbon chains, aromatic rings, or halogen atoms, the resulting polymer lacks flexibility. The requirement for flexibility is met by the above-mentioned polyethylene glycol di(meth)acrylate for cast polymerization which has the polyether structure. This polymer, however, has a water absorption as high as 10-20%.